Countertop oven



FIG. 1 is a perspective view taken from the front, top and right side of a countertop oven showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a top plan view thereof. 

The ornamental design for a countertop oven, as shown and described. 